Choose the incorrect acid-source pair?

Appeared in: NIA - 29 January 2023

Explanation

The pair 'Oxalic acid - Ant sting' is factually incorrect.
Ant stings contain Formic acid (also known as Methanoic acid), which is responsible for the sharp pain and irritation.
Oxalic acid is a different organic acid found naturally in many plants, such as spinach, rhubarb, and tomatoes, but it is not present in ant stings.

Option A: This is a correct pairing. Citric acid is a primary acid found in citrus fruits like lemons, contributing to their sour taste.
Option B: This is a correct pairing. Lactic acid is produced from the fermentation of lactose in milk, which causes milk to sour and is the basis for products like yogurt and curd.
Option D: This is a correct pairing. Methanoic acid (more commonly known as formic acid) is a key component of the venom injected by nettle stings, causing a characteristic burning sensation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Common organic acids and their natural sources as background academic context rather than a clinical decision trigger.
Understanding acid sources is fundamental in toxicology and first aid. Knowing that ant and nettle stings are acidic helps in understanding why applying a mild base like baking soda solution can provide relief.
Dietary awareness of acids like oxalic acid is important for patients with a history of kidney stones, as high oxalate intake can contribute to the formation of calcium oxalate stones.
What if? If a patient presents with skin irritation after gardening, knowing the difference between a nettle sting (formic acid) and contact dermatitis from a plant like poison ivy (urushiol oil) is crucial for recommending the correct treatment (a mild base for the sting vs. corticosteroids for the dermatitis).

How to Approach the Question

First, carefully read the question and identify the core task. The keyword here is 'incorrect', meaning you are looking for the one false statement among the options.
Analyze each option by evaluating the relationship between the acid and its given source.
Option A: Citric acid is famously associated with citrus fruits like lemons. This is a well-known fact, so this pair is correct.
Option B: Lactic acid is related to lactose, the sugar in milk. Its presence in sour milk is a standard example of fermentation. This pair is correct.
Option C: Consider the chemical in an ant sting. The burning sensation is caused by formic acid (methanoic acid). Therefore, pairing it with oxalic acid is incorrect.
Option D: Nettle stings are also known to contain formic acid (methanoic acid). This pair is correct.

Concept Tested & Keywords

Concept Tested: Common organic acids and their natural sources
Stem keywords: acid-source pair, Citric acid, Lactic acid, Oxalic acid, Methanoic acid
Lead-in keywords: incorrect
Negative lead-in flag: The question asks for the INCORRECT pair.

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E6 Physiology Guyton 4SAE Part 3 p. 120-122

Practise the full NIA - 29 January 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.